Proteins stabilized with polysaccharide gums

ABSTRACT

Described are heat stable aqueous solutions or gels comprising a biologically effective amount of a protein and an effective stabilizing amount of a polysaccharide gum as well as heat stable solutions or gels suitable for use in an implantable drug delivery device at body temperature. Also disclosed are lyophilized compositions having biologically activity, where such lyophilized compositions are formed by lyophilozing the stabilized solutions or gels of the invention. Such lyophilized powders can be used after reconstitution with an amount of aqueous that provide an effective stabilizing concentration of polysaccharide and a pharmaceutically acceptable amount of therapeutic protein particularly against thermal and oxidative stress.

[0001] This application claims the benefit of U.S. application Ser. No.10/012,667 filed Oct. 30, 2001, the content of which is incorporatedherein by reference as if completely rewritten herein.

TECHNICAL FIELD

[0002] The present invention relates to a heat stable aqueous solutionor gel comprising a biologically effective amount of a protein and aneffective stabilizing amount of a polysaccharide gum as well as heatstable solutions or gels suitable for use in an implantable drugdelivery device. This invention also relates to lyophilized compositionshaving biological activity, where such lyophilized compositions areformed by lyophilizing the stabilized solutions or gels of the inventionas well as the lyophilized compositions that are reconstituted in anaqueous buffer so as to provide a high concentration of polysaccharidesthat will stabilize proteins under physiological conditions.

BACKGROUND OF THE INVENTION

[0003] The commercial market for recombinant protein biopharmaceuticalsis expanding rapidly as various biotechnology and pharmaceuticalcompanies develop and test biologically active proteins. The emergingfield of proteomics will likely provide protein targets useful for drugdevelopment, thereby enabling the market for recombinant proteinbiopharmaceuticals to continue its expansion.

[0004] Currently, proteins are utilized in a variety of diagnostic andtherapeutic applications. For example, one protein used in a diagnosticapplication is the enzyme glucose oxidase, which is used in glucoseassays. The hormone insulin is an example of a protein utilized intherapeutic applications. However, proteins are particularly sensitiveto certain environmental conditions and may not be stable at elevatedtemperatures, including physiological temperature of 37° C., innon-optimal aqueous solvent systems, or in organic solvent systems.Protein stability may also be affected by pH and buffer conditions andexposure to shear forces or other physical forces.

[0005] The stability of a protein refers to both its conformationalstability, which is reflected in the protein's three-dimensionalstructure, and its chemical stability, which refers to the chemicalcomposition of the protein's constituent amino acids. Proteininstability can result in a marked decrease or complete loss of aprotein's biological activity. Deleterious stresses such as organicsolvents, extremes of pH, high temperatures, and/or dehydration (drying)can affect both the conformational and chemical stability of a protein.Chemical instability can result from processes such as (a) deamidationof the amino acids residues asparagine or glutamine, (b) oxidation ofcysteine or methionine amino acid residues, or (c) cleavage at any ofthe peptide amide linkages of the protein. Examples of conformationalinstability include aggregation (fibrillation), precipitation, andsubunit dissociation.

[0006] Because an inactive protein is useless, and in some casesdeleterious, for most diagnostic and therapeutic applications, there isa need for a means by which proteins can be stabilized in solution atelevated temperatures (e.g. at and above room temperature, at bodytemperature or higher. It is known in the art that proteins can bestabilized in solution by the addition of soluble excipients thatstabilize the monomeric, correctly folded protein conformation.Disaccharides such as trehalose, sucrose, or lactose, and surface activeagents such as phospholipids, Tween, and Triton are examples ofexcipients useful for stabilizing proteins. These stabilizers must beused in non-toxic levels because in the case of therapeutic proteins,the stabilizers are necessarily administered to the patient with theprotein.

[0007] U.S. Pat. No. 5,834,273 issued to Futatsugi et al. on Nov. 10,1998 provides a heat and protease resistant enzyme with improved storagestability. This enzyme is modified with a polysaccharide, polyaminoacid, or synthetic polymer having a plurality of carboxyl groups bymeans of a crosslinking agent capable of binding both carboxyl groupsand amino groups.

[0008] U.S. Pat. No. 5,736,625 issued to Callstrom et al. on Apr. 7,1998 discloses a method for preparing water soluble, saccharide-linkedprotein polymer conjugates that stabilize the protein in a hostileenvironment. The claimed method includes covalently binding the polymerto the protein through at least three linkers, each linker having threeor more hydroxyl groups. The protein is conjugated at lysines orarginines.

[0009] U.S. Pat. No. 5,691,154 issued to Callstrom et al. on Nov. 25,1997 provides an enzyme linked immunoassay in which the enzyme is in theform of a water soluble polymer saccharide conjugate which is stable inhostile environments. The conjugate includes the enzyme which is linkedto the polymer at multiple points through saccharide linker groups.

[0010] U.S. Pat. No. 5,612,053 issued to Baichwal et al. on Mar. 18,1997 discloses an inhalable powder formulation which includes cohesivecomposites of particles containing a medicament and a controlled releasecarrier which includes one or more polysaccharide gums of naturalorigin.

[0011] U.S. Pat. No. 5,492,821 issued to Callstrom et al. on Feb. 20,1996 discloses water soluble protein polymer conjugates in whichproteins linked to an acrylic polymer at multiple points by means ofsaccharide linker groups. These conjugates are also stable in hostileenvironments.

[0012] U.S. Pat. No. 5,128,143 issued to Baichwal et al. on Jul. 7, 1992provides, for oral delivery, a slow release pharmaceutical excipient ofan inert diluent and a hydrophilic material including xanthan gum and agalactomannan gum capable of cross-linking the xanthan gum in thepresence of aqueous solutions.

[0013] Ispas-Szabo et al. demonstrated that the ability of starchtablets to swell and release low molecular weight drugs could becontrolled by the degree that the starch was cross-linked. No datarelated to protein stabilization was presented. Carbohydrate Research323, 163-175 (2000).

[0014] Artursson et al. demonstrated that proteins could be incorporatedinto polyacryl starch microparticles. One incorporated protein, theenzyme carbonic anhydrase, retained a low amount of activity attemperatures where the free protein had no activity (e.g., >70° C.). Atlower temperatures (e.g., <65° C.), however, the free enzyme was morestable than the enzyme incorporated into the microparticles. Journal ofPharmaceutical Sciences 73, 1507-1513 (1984).

[0015] Gliko-Kabir et al. demonstrated that the swelling of lyophilizedguar gum powder in gastric or intestinal buffer could be reduced fromapproximately 100 fold to approximately 5 fold if the guar wascrosslinked with glutaraldehyde. No data concerning proteinstabilization was presented. Pharmaceutical Research 15,1019-1025(1998).

[0016] Bauman et al. demonstrated that carrageenan gum stabilized theenzyme cholinesterase against heat when the enzyme was dried on aurethane foam sheet with 8% starch. Analytical Biochemistry 19, 587-592,(1967).

[0017] U.S. Pat. No. 6,391,296 Bl issued to Toray Industries, Inc. onMay 21, 2002 and European Patent Application No. EP 0 950 663 A1submitted by the same company and published on Oct. 20, 1999 disclosethe use of gum arabic as a protein stabilizer. Aqueous solutionscontaining 0.2%-2% gum arabic were shown in these documents to stabilizeproteins to storage at 4° C. and to freeze drying. There was no data andno discussion concerning the ability of gum arabic to stabilize proteinsat room temperature or higher temperatures. While the examples cite theuse of gum arabic at 0.2%-2%, the US patent claims the use of gum arabicfrom 0.2% to 10%. No mention is made of possible benefits to using gumarabic as a stabilizer at concentrations greater than 10% or atphysiological temperature, pH, or salt concentration.

[0018] Many of the methods that are known to stabilize proteins, requirethat the protein be covalently attached to a solid support or covalentlysubstituted with a stabilizing molecule. Covalent modification is notalways practical for proteins in solutions and can change the biologicaleffectiveness of a therapeutic protein., Thus there is a need for aprotein stabilization system that does not require covalent modificationof the protein.

[0019] The typical method of administering therapeutic proteins to apatient or test subject is by means of needle-based injections.Currently, many pharmaceutical and drug delivery companies are seekingto develop alternative systems for the delivery of therapeutic proteins.These alternative systems are expected to require fewer dosings and toallow for more effective control over the rate of protein release in thebody.

[0020] One alternative drug delivery system known in the art includesthe formulation of the protein in a biodegradable, water insoluble,polymer matrix. The polymer (e.g., poly(lactic-co-glycolic acid)) can beformulated as an injectable or respirable microparticle. Alternately,the protein can be formulated in a temperature sensitive polymer that isliquid at room temperature but solidifies at 37° C. after injection intoa patient. A third alternative is for the polymer to be dissolved in anon-toxic water miscible solvent that dissolves in plasma afterinjection leading to precipitation of the polymer. In all cases, thepolymer systems are developed for sustained release of protein overtime; however, the stability of the protein during the release period isdifficult to maintain and generally less than 50% of the total proteinload can be delivered. Additionally, the delivery of the protein is notuniform, but rather occurs with a rapid initial burst which is followedby a much slower rate of sustained protein release.

[0021] A second type of known delivery system includes an implanted pumpsuch as an osmotic pump. In this system, a suspension of protein in awater miscible organic solvent is continuously delivered to the patientor test subject through an orifice in the osmotic pump implant. However,use of this system may prove problematic because it is often difficultto suspend a high protein load in the organic solvent, and only someproteins are stable to prolonged incubation under the requirednon-aqueous or mixed organic-aqueous conditions.

[0022] Thus, given the current state of the art, there is a need forcompositions and methods that effectively stabilize a variety ofproteins in various chemical and physical environments, and that arecompatible with a variety of drug delivery systems.

SUMMARY OF THE INVENTION

[0023] The present invention is directed to stable aqueous solutions andgels of biologically active proteins wherein the protein solutions andgels are stabilized by high molecular weight polysaccharide gums. Thestable protein solutions and gels may be used in drug delivery systemsand are protected against stresses such as high temperatures, oxidation,organic solvents, extremes of pH, drying, freezing, and agitation.Preferably, in the solutions and gels of the invention, thepolysaccharide gums are not bound to the protein.

[0024] According to a preferred embodiment, the aqueous solutions orgels of the invention include at least one biologically active protein,wherein the protein may be an enzyme, antibody, hormone, growth factor,or cytokine and at least one polysaccharide gum for stabilizing theprotein, wherein the polysaccharide gum may be, for example, gum arabic,guar gum, xanthan gum, locust bean gum, gum ghatti, gum karaya,tragacanth gum or a related polysaccharide.

[0025] Drug delivery systems compatible with the present inventioninclude implanted subcutaneous delivery systems and intravenous drugdelivery systems that can actively or passively deliver the biologicallyactive proteins.

[0026] In one embodiment of the present invention, high molecular weightpolysaccharide gums are used to stabilize therapeutic proteins deliveredby means of implanted drug delivery devices such as a capsule, whereinthe capsule includes a molecular weight cut-off membrane with uniformpore size. The polysaccharide gum stabilizes the protein contained bythe capsule and the release of the protein can be controlled by themembrane which is permeable to the therapeutic protein but impermeableto the higher molecular weight gum. This embodiment, therefore, wouldnot necessarily be compatible with small molecular weight stabilizersthat would diffuse out of the capsule faster than the protein. Themembrane retains the polysaccharide gum in the capsule and the capsuleprevents the gum from swelling and decreasing in concentration.

BRIEF DESCRIPTION OF THE FIGURES

[0027]FIG. 1 shows the ability of gum arabic to stabilize interferon-γunder physiological conditions over 4 weeks.

[0028]FIG. 2 shows the ability of gum arabic to stabilize lactatedehydrogenase (LDH) against oxidative stress by copper and ascorbicacid.

[0029]FIG. 3 shows the ability of gum arabic to stabilize lactatedehydrogenase against oxidative stress by copper, ascorbic acid, andhydrogen peroxide.

[0030]FIG. 4 is a schematic diagram of a capsule with a semi-permeablemembrane.

[0031]FIG. 5 is a tabular presentation of chymotrypsin release in 48hours through a 100K membrane.

[0032]FIG. 6 is a schematic diagram of the apparatus used to generatethe chymotrypsin data for FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention is directed to a heat stable aqueoussolution or gel comprising a biologically effective amount of a proteinand a stabilizing effective amount of a polysaccharide gum material. Theinvention is further directed to a heat stable aqueous solution or gelcomprising a biologically effective amount of a protein and astabilizing effective amount of a polysaccharide gum material whereinsaid protein is selected from the group consisting of an enzyme, anantibody, a hormone, a growth factor, and a cytokine wherein said gum isselected from the group consisting of gum arabic, guar gum, xanthan gum,locust bean gum, gum karaya, gum ghatti, and tragacanth gum.

[0034] Another embodiment of the invention relates to a heat stablesolution or gel comprising a pharmaceutically effective amount of aprotein and a stabilizing effective amount of a gum material whereinsaid stabilized solution or gel is contained in an implantable drugdelivery device.

[0035] A further embodiment of the invention is directed to alyophilized composition having biological activity, wherein saidlyophilized composition is formed by lyophilizing a heat stable solutionor gel comprising a biologically effective amount of a protein and astabilizing effective amount of a gum material. In a preferredembodiment, the lyophilized dry powder is reconstituted in an aqueousbuffer to give a high concentration of gum, wherein the gumpreferentially stabilizes the protein to various stresses underphysiological conditions. As used herein the term “biologically activeprotein” includes proteins and polypeptides that are administered topatients as the active drug substance for prevention of or treatment ofa disease or condition as well as proteins and polypeptides that areused for diagnostic purposes, such as enzymes used in diagnostic testsor in in vitro assays as well as proteins that are administered to apatient to prevent a disease such as a vaccine. Contemplated for use inthe compositions of the invention, but not limited to, are therapeuticproteins and polypeptides such as enzyrmes, e.g., glucocerebrosidase,adenosine deaminase; antibodies, e.g., Herceptin® (trastuzumab),Orthoclone OKT®3 (muromonab-CD3); hormones, e.g., insulin and humangrowth hormone (HGH); growth factors, e.g., fibroblast growth factor(FGF), nerve growth factor (NGF), human growth hormone releasing factor(HGHRF), and cytokines, e.g., leukemia inhibitory factor (LIF),granulocyte-colony stimulating factor (G-CSF),granulocytemacrophage-colony stimulating factor (GM-CSF), interleukin-6(IL-6), interleukin-11 (IL-11), interleukin-9 (IL-9), oncostatin-M(OSM), ciliaryneurotrophic factor (CNTF), interferon-(x, andinterferon-γ. As used herein, the Polysaccharide Solubility Limit is theconcentration of polysaccharide obtained after an aqueous buffer,typically a phosphate buffered saline (PBS) is slowly added to a solidpolysaccharide, with thorough mixing, until all of the solid materialhas either dissolved or has hydrated to form a gel. Depending on thepolysaccharide used, the solubility limit can be in the vicinity of 10%or can be higher than 50%. Physiological condition as pertained to thisinvention is typically human body temperature under normal conditions,that is, 37° C. a neutral pH of around 7+1, and a physiologicalconcentration of saline (0.9%).

[0036] The term “pharmaceutically effective amount” refers to thatamount of a therapeutic protein having a therapeutically relevant effecton a disease or condition to be treated. A therapeutically relevanteffect relieves to some extent one or more symptoms of a disease orcondition in a patient or returns to normal either partially orcompletely one or more physiological or biochemical parametersassociated with or causative of the disease or condition. Specificdetails of the dosage of a particular active protein drug may be foundin the drug labeling, i.e., the package insert (see 21 CFR § 201.56 &201.57) approved by the United States Food and Drug Administration.

[0037] Polysaccharide gums are natural products extracted from variousplants, trees and bacteria, such as Cyamopsis tetragonolobus (guar gum)and Ceratonia siliqua (locust bean or carob gum) and Astragalus gummifer(tragacanth) from plants of the Leguminosae family; gum arabic andtamarind gum from respectively the Acacia senegal tree and Tamarindusindica tree; xanthan gum from the bacterial genus Xanthamonascampestris; gum ghatti from Anogeissus latifolia and gum karaya fromSterculia urens. Many grades and forms of polysaccharide gums arecommercially available.

[0038] The gum Arabic used in the solutions of the invention has ahighly branched galactose core with linkages to other sugars andcontains ˜1% glycoprotein; the locust gum used herein has a mannan chain(1->4) with galactose substituted at the 6-position of ˜20% of themannose units; the guar gum used herein has a mannan chain (1->4) withgalactose substituted at the 6-position of −40% of the mannose units;and the xanthan gum used herein has a glucan (1->4) chain withtrisaccharides substituted on every other glucose.

[0039] According to the preferred embodiment of the present invention,increasing concentrations of high molecular weight polysaccharide gums(i.e., greater than 200 kilodaltons) are utilized for effective proteinstabilization. The polysaccharide gums described herein are moreeffective protein stabilizers than commonly used small molecule proteinstabilizers such as monosaccharides, disaccharides, and detergents. Highmolecular weight, branched chain or substituted polysaccharides such asgum arabic, guar gum, xanthan gum, and locust bean gum are moreeffective protein stabilizers than linear chain polysaccharides such ascellulose, agarose, xylan, konjak, or chitosan. The polysaccharide gumsused herein are typically used at concentrations of gum (% w/v) that arenear or at the upper limit of the solubility of the particular gum inaqueous solutions. The gums used herein will form either a viscoussolution in water or will form a gel. In general, from about 0.5% tofrom about 35% weight to volume (“w/v”) will be used depending on theparticular polysaccharide. Gum arabic has exceptional solubility inaqueous solution and up to about 50% formulations have been made.Preferred are gum arabic concentrations above 10%, concentrations above20% give are more preferred, while concentrations above 30% are yet morepreferred, and concentrations above 40% are the most preferred as thesehave resulted in the greatest stability in many of the tests herein. Ina preferred embodiment, stabilizing gum concentrations should providestabilities above 70% protein activity under physiological conditions(at 37° C.) for at least about a two weeks and most preferably, forpatient ease of use, at least 1 month or more. Recent tests have shownthat gum arabic concentrations of about 50% provide about fullinterferon-gamma activity after 1 month and that 45% activity was stillavailable after two months at physiogical condtions (refer to Table 9).

[0040] Polysaccharide gums are hydrogels that can absorb many timestheir weight of water. Therefore, it is preferable to restrict thetendency of the gums to swell in order to maintain the highpolysaccharide concentrations that effectively stabilize proteins. Thehigh gum concentration can be maintained by enclosing the gels in acapsule with a molecular membrane that is permeable to the protein butimpermeable to the higher molecular weight gum. The capsules can beimplanted into a patient or test subject for the controlled release ofstabilized protein over extended periods. Over time, the protein issteadily released from the capsule thus, decreasing the concentration ofprotein inside the capsule while the concentration of the stabilizinggum within the capsule remains constant.

[0041] The present invention includes polysaccharide gums that areincorporated into drug delivery devices for the purposes of (i)stabilizing proteins and (ii) controlling the rate at which the proteinsdiffuse from the delivery device. The polysaccharide gums of the presentinvention stabilize native protein conformations, even at high proteinconcentrations. Thus, the delivery device can be loaded with aprotein/gum composition that contains a high concentration of protein,or with a mixture in the solid form, thereby increasing the drug load ofthe device.

[0042] In various embodiments, the compositions of the present inventionare utilized for the stabilization of proteins duringmembrane-controlled release from capsules or other devices implantedinto a patient or test subject. In this case, the delivery device isdesigned to prevent the polysaccharide from swelling so that thestabilizing effects of high polysaccharide concentrations are maintainedinside the capsule. Since it is unnecessary for the polysaccharide gumsdescribed herein to bind to proteins to effect protein stabilization,proteins can be released from the solution or gel by diffusion.Additionally, the polymeric properties of polysaccharide gums provide anadditional mechanism for stabilizing proteins by restricting a protein'smolecular mobility.

[0043] The physical state of the polysaccharide gums of the presentinvention depends on the conditions used to prepare the gum solutions.Viscosities can vary several fold for each gum depending on factors suchas the mixing rate used to prepare the hydrated gum and whether the gumwas heat treated or freeze-thawed. Manipulating the viscosity of thegums will permit the rate at which proteins are released from the gumsto be controlled, as the rate of diffusion is inversely proportional tothe solution viscosity.

[0044] The stabilized protein solutions and gels of the invention maycontain minor amounts (from about 0.5% to about 5.0% w/v) of auxiliariesand/or excipients, such as N-acetyl-dl-tryptophan, caprylate, acetate,citrate, glucose and electrolytes, such as the chlorides, phosphates andbicarbonates of sodium, potassium, calcium and magnesium. They canfurthermore contain: acids, bases or buffer substances for adjusting thepH, salts, sugars or polyhydric alcohols for isotonicity and adjustment,preservatives, such as benzyl alcohol or chlorobutanol, andantioxidants, such as sulphites, acetylcysteine, Vitamin E or ascorbicacid.

[0045] Suitable tonicity adjustment agents may be, for instance,physiologically acceptable inorganic chlorides, e.g. sodium chloride;sugars such as dextrose; lactose; mannitol; sorbitol and the like.Preservatives suitable for physiological administration may be, forinstance, esters of parahydroxybenzoic acid (e.g., methyl, ethyl, propyland butyl esters, or mixtures of them), chlorocresol and the like.

[0046] The pH of the solution can be adjusted using a physiologicallyacceptable acid e.g. an inorganic mineral acid such as hydrochloric,hydrobromic, sulfuric, phosphoric, nitric and the like, or an organicacid such as acetic, succinic, tartaric, ascorbic, citric, glutamic,benzoic, methanesulphonic, ethanesulfonic and the like, or aphysiologically acceptable base, such as sodium hydroxide, potassiumhydroxide, calcium hydroxide, magnesium hydroxide and the like, anphysiologically acceptable buffer solution, e.g. a chloride buffer, anacetate buffer, a phosphate buffer and the like.

[0047] In another embodiment of the present invention, the drug deliverydevice is a capsule that is filled with multiple layers ofpolysaccharide gums of varying viscosities. This capsule includes amolecular membrane capable of retaining the gum, but which is permeableto various therapeutic proteins. In this embodiment, a layer of viscousgum (e.g., guar gum) adjacent to the polymer membrane controls therelease of the protein, while a layer of less viscous gum (e.g., gumarabic) that has been formulated with the protein provides a stablereservoir of protein.

[0048] In still another embodiment, hollow fibers with specificallydefined molecular weight cutoffs are filled with solutions or gels ofgum and protein. Hollow fibers with controlled pore sizes are useful forrapidly dialyzing proteins. Preferably, the fibers are made ofbiocompatible materials that can be implanted in a patient or testsubject. The fibers may be filled with solutions of protein formulatedwith guar gum or with locust gum. The gums control the rate of proteinrelease as well as providing protein stabilization during release.Because the hollow fibers have a very large surface area to volumeratio, this approach is most useful for gum/protein gels with slowprotein diffusion rates. A positive attribute of an implant thatcontains multiple hollow fibers is that all the therapeutic protein willnot be in the same capsule, thereby lessening the possibility of acapsule failure, which might release a toxic dose of the protein.

[0049] An alternate embodiment of hollow fibers includes the steps offilling the hollow fibers with a gum arabic/protein solution andimbedding multiple fibers in a matrix of guar or locust gums. The guaror locust matrix is then enclosed in a dialysis membrane or a membraneenclosed capsule. This embodiment has many of the stabilization anddiffusion properties of the multi-layered capsule approach, but in thiscase the main drug load is not in a single capsule and is, therefore,less vulnerable to a single capsule failure.

[0050] According to the present invention, a preferred method forstabilizing a therapeutic protein in a drug delivery system comprisesthe steps of (a) providing a protein as an aqueous solution; (b) addinga polysaccharide gum to the protein; and (c) adding the gum/proteinsolution or gel to a capsule that contains a molecular membrane.Alternatively, the protein/polysaccharide gum can be dried bylyophilization or spray drying and added to the capsule. In this method,the capsule is preferably fabricated from a biocompatible material andcapable of containing the polysaccharide gum in a fixed volume toprevent the gum from swelling upon exposure to an aqueous environment.The capsules comprise a single large protein reservoir or may becomprised of a plurality of hollow fibers. The membrane is fabricatedfrom silica or a polymer and has pore sizes, which permit the membraneto be permeable to the protein but impermeable to the higher molecularweight polysaccharide gum. The polysaccharide gum is selected based onits ability to both stabilize the protein and control the protein's rateof release. In this method, multiple gums and multiple layers of gumscan be used in the capsule.

[0051] The following examples illustrate the effectiveness of thecompositions and methods of the present invention in stabilizingproteins under different environmental conditions and in different modeldelivery systems.

EXAMPLE 1

[0052] A 1 mg/ml solution of chymotrypsin was made by dissolving 20 mgsof chymotrypsin in 20 mL of phosphate buffered saline (PBS, pH 7.4).Solutions of the gums containing chymotrypsin were made as follows: 1.66ml of 1 mg/mL chymotrypsin solution in PBS was added to 0.83 g of gumarabic and homogenized to give a 33% gum arabic solution by weight,using the assumption that 1 mL of the chymotrypsin/PBS solution willapproximately be equal tol gram. A similar procedure was repeated for33% sorbitol. To 0.5 g of tragacanth gum, gum guar or xanthan gum, 2 mlof 1 mg/mL chymotrypsin in PBS was added and homogenized to give a 20%solution. To 0.625 g of gum karaya and gum ghatti, 1.875 mL of 1 mg/mLchymotrypsin in PBS was added and homogenized to give a 25% solution.Similarly, to 0.35 g of locust bean gum, 2.15 mL of 1 mg/mL chymotrypsinin PBS was added and homogenized to give a 14% solution. The pH of allthe solutions, except 33% sorbitol, was adjusted to 7.4 using 1 M NaOH.All the samples (33% gum arabic, 33% sorbitol, 20% tragacanth gum, 20%gum guar, 20% xanthan gum and 14% locust bean gum) were prepared in 50mL centrifuge tubes and incubated at 60° C. for 7.5 min in a water bath.The samples were cooled on ice and diluted 20-fold in order to give afinal concentration of 0.05 mg/mL chymotrypsin. Dilutions were performedby adding 31.73 mL PBS to the 33% gum solutions, 35.625 mL for the 25%gum solutions, 38 ml PBS for the 20% gum solutions 5 and 40.85 mL PBS tothe 14% gum solution. These solutions were homogenized before assayingthem for chymotrypsin activity using N-benzoyl L-tyrosine ethyl ester asthe enzyme substrate according to published literature (J. Biotech,1994, v35, p9-18). The results are summarized in Table 1. TABLE 1 TheEffect of Polysaccharides on the Stability of the Enzyme ChymotrypsinIncubated at 60° C. for 7.5 Minutes Concentration of Stabilizer %Recovery % Recovery Stabilizer (% w/v) 60° C. Room Temp. None — 0% 100%Sorbitol 33% ˜27% ˜90% Gum Arabic 33% ˜98% ˜100% Locust Gum 14% ˜85%˜100% Guar Gum 20% ˜92% ˜100% Xanthan Gum 20% ˜50% ˜100% Tragacanth gum20% ˜68% ˜100% Gum Karaya 25% ˜30% ˜75% Gum Ghatti 25% ˜30% ˜100%

[0053] As shown in Table 1, an accelerated aging study performed at 60°C., gum arabic, guar gum, xanthan gum, locust bean gum and tragacanthgum all stabilized the activity of the enzyme chymotrypsin over 50%.Recoveries are significantly higher than those obtained by incubationwith sorbitol, a monosaccharide shown in the literature to stabilizechymotrypsin. Other gums such as gum karaya and gum ghatti, stabilizedchymotrypsin activity around 30%.

[0054] As indicated in Example 1, chymotrypsin is stabilized at 60° C.by high concentrations of gum arabic, guar gum, xanthan gum, tragacanth,gum karaya, gum ghatti and locust gum. The stabilizing effects of gumarabic, xanthan gum, locust gum, and guar gum were found to decrease asthe gum concentration decreased, as shown in Table 2. TABLE 2 The Effectof Different Polysaccharide Concentrations on the Stability of theEnzyme Chymotrypsin Incubated at 60° C. for 7.5 Minutes % Recovery ofChymotrypsin Activity^(a) 30% 20% 15% 10% 5% 2.5% 1% Gum Gum Gum Gum GumGum Gum Gum Arabic 92% ND 38% ND ND ND ND Guar ND 58% 33% 27% 12%  4% 0% Xanthan ND 46% 31% 26% 14%  3%  0% Locust ND ND  70%^(b) 48% 26% 24%14%

[0055] Following the procedure of Example 1, other polysaccharides andtwo surfactants were tested. None of the materials listed in Table 3were effective to stabilize aqueous solutions of chymotrypsin againstelevated temperatures. TABLE 3 Polysaccharides and Surfactants that donot Stabilize Chymotrypsin at 60° C. Concentration of Sugar orSurfactant Additive (% w/v) Structure Cellulose 25% Linear β1,4-glucosechain Agarose 14% Linear chain of galactose and anhydro-galactoseBeechwood 50% Linear xylose chain Xylan Barley Beta 17% β1,3-glucanchain Glucan Konjak 25% Linear chain of glucose + mannose GlucomannanChitosan 17% Linear chain of anhydro-N-acetyl glucosamine Amylopectin33% Branched glucose chain Untreated 33% Branched amylopectin + linearStarch amylose Hydroxyethylstarch 33% Starch chemically modified withhydroxyethyl groups Dextran 33% α 1,6-anhydro-D-glucose chain Tween 201% Polyoxyethylene(20)sorbitan monolaurate Tween 80 1%Polyoxyethylene(20)sorbitan monooleate

[0056] Following the procedures described in Example 1, theconcentration of chymotrypsin the solution was varied and theconcentration of gum Arabic was held at 33% (w/v) in the solution. Theresults are summarized in Table 4. TABLE 4 Stabilization of IncreasingConcentrations Of Chymotrypsin by Gum Arabic Gum Arabic ChymotrypsinConcentration Concentration % Activity (% w/v) (mg/ml) 7.5 Min., 60° C.0 1.0 0 0 3.3 0 0 10. 0 0 33. 0 0 100 0 33% 1 97 ± 17%^(a) 33% 3.3 62 ±6%^(a) 33% 10 57 ± 5%^(a) 33% 33 41%^(b) 33% 100 53%^(b)

EXAMPLE 2

[0057] Gum arabic (33%) chymotrypsin solutions were prepared asdescribed in Example 1, with the exception that PBS was made with 0.1%sodium azide. A solution containing 1 mg/ml chymotrypsin and no gumarabic was prepared as the control. Aliquots of the test and controlsolutions were added to centrifuge tubes and these tubes were incubatedat 37° C. for a period of time. The results are summarized in Table 5.TABLE 5 Chymotrypsin Stabilization at 37° C. by 33% (w/v) Gum ArabicTime Stabilizer Weeks % Activity Control (None) 0 100 Control 1 15Control 2 0 Control 4 0 Gum Arabic 1 130 Gum Arabic 2 80 Gum Arabic 4 82Gum Arabic 8 58

[0058] As shown in Table 5, gum arabic was tested for its ability tostabilize chymotrypsin to long-term incubation at 37° C. in aqueousbuffer, pH 7.4 (physiological conditions). The results shown in Table 5indicate that gum arabic protects chymotrypsin and only approximately40% of the activity of chymotrypsin is lost after incubation at 37° C.for eight weeks. In contrast, 85% of the activity is lost after one weekand all the activity is lost after the second week at 37° C. in theabsence of stabilizer.

[0059] It is important that the concentration of the gum stabilizer inthe aqueous solution be high enough to effectively stabilize theprotein. The stabilization of the particular protein is dependent on theconcentration of polysaccharide gum in the solution. As shown in Table6, the activity of chymotrypsin exposed to heat stress depends on theconcentration of gum, with higher concentrations giving betterstability. TABLE 6 High Gum Concentrations are Required for OptimalProtein Stabilization Concentration (% w/v) % Activity Recovered Of GumArabic 1 Week, 37° C. None 0 33 73 20 85 10 62  5 43  2.5 21  1.0 17

[0060] As indicated in Table 6, gum arabic is a stabilizer ofchymotrypsin from 1% to 33%. guar gum has been found to providestabilization to chymotrypsin at a concentration of about 2.5 to 20%(w/v), xanthan gum and tragacanth gum provide stabilization at aconcentrations of about 1.5 to 20% (w/v), gum karaya and gum ghatti areeffective in the concentration range of 1 to 25% and locust gum iseffective at a concentration of about 1 to 14% (w/v). However,concentrations of gum arabic typically above 10% (w/v) are required foreffective use in medical and industrial settings. Typically from one toseveral weeks, or months of stability are preferred.

[0061] The polysaccharide gum stabilizers described herein, not only areable to stabilize proteins in solution but are also able to protect suchproteins through conventional lyophilization and subsequentreconstitution. In a preferred application, the reconstitution of alyophilized mixture of gum and protein is carried out in a manner as tomaintain the high concentrations of the gum. Example 3, describes thepreparation of an aqueous solution of the enzyme lactate dehydrogenase(LDH), an enzyme that loses its activity when lyophilized and thenreconstituted.

EXAMPLE 3

[0062] A 1 mg/mL solution of lactate dehydrogenase (LDH) was prepared bydissolving 5 mgs LDH in 5 mL of PBS, pH 7.4. A 10 μg/mL stock solutionof LDH was prepared by dissolving 200 μL of 1 mg/mL LDH solution in 19.8mL PBS. The gum solutions with LDH were prepared as follows: to 0.25 gof each gum or sorbitol, 2.25 mL of 10 ptg/mL LDH was added andhomogenized. Aliquots of 1 mL in plastic Eppendorf tubes were frozen at−70° C. for 30 min and lyophilized overnight using a Labconco model77530 lyophilizer. To each tube of the LDH lyophilizate, 2.25 mL waterwas added to give a reconstituted solution of 10 pg/ml enzyme. Thereconstituted lactate dehydrogenase was assayed for activity using thepublished literature method of Lovell and Winzor (Biochemistry, 1974,v13, 3527). The results are summarized in Table 7. TABLE 7 Stabilizationof Lyophilized Lactate Dehydrogenase (LDH)^(a) Concentration BeforeStabilizer Lyophilization % Activity Recovered None 10 20 Sorbitol 10 20Gum Arabic 10 64 Xanthan gum 10 37 Locust Bean Gum 10 93 Agarose 10 59Guar Gum 10 78

[0063] As shown in Table 7, polysaccharide gums were tested for theirability to stabilize lactate dehydrogenase, an enzyme that losesactivity when lyophilized. Both the gums that were effective thermalstabilizers (i.e., gum arabic, guar gum, xanthan gum, locust bean gum)and a gum that provided no thermal stabilization (i.e., agarose) wereeffective stabilizers of lactate dehydrogenase during the lyophilizationprocess. This result indicates that polysaccharide gums are effectivestabilizers of a lyophilized protein and shows that the gums can be usedto protect therapeutic proteins that are lyophilized prior to theiraddition to a drug delivery device. The protein/polysaccharide powdermay be added to the delivery device dry, as a solution, as a gel, or asslurry. The lyophilized protein-polysaccharide gums powder will beuseful for long term shelf storage of therapeutic proteins as well. Inanother embodiment, the lyophilized powder will be stable in aqueousbuffer solution when it is reconstituted if a high enough concentrationof polysaccharide gum is present in the lyophilized powder or if anadditional amount is added later. Preferably the lyophilized powder willcontain a sufficient concentration of gum to stabilize the materialbefore and after reconstitution.

Example 4

[0064] Following the procedure described in Example 1, solutions oflysozyme (1 mg/mL), lactate dehydrogenase (50 μg/mL), andglucose-6-phosphate dehydrogenase (50 μg/mL) were subjected toaccelerated aging at respectively 90° C., 60° C., and 50° C., and for 10minutes each. The activity of lactate dehydrogenase was assayed inaccordance with the procedure of Lovell and Winzor (Biochemistry, 1974,v13, 3527) described in Example 3. The activity of glucose-6-phosphatedehydrogenase was assayed using the method published in Arch. Biochem.Biophys, 1998, v360, p10-14. The activity of lysozyme was assayedaccording to the method published in Biochimica et Biophysica Acta,1952, v8, p 302-309. The results are summarized in Table 8. TABLE 8Thermal Stabilization of Lactate Dehydrogenase, Glucose-6-PhosphateDehydrogenase, and Lysozyme By Polysaccharide Gums Conc. of Accelerated% Conc. of Stabilizer Aging Acti- Protein Protein Stabilizer (% w/v)Conditions vity Lysozyme  1 mg/mL None 0 90° C.; 5 10 min Lysozyme  1mg/mL Gum 33 90° C.; 85 Arabic 10 min Lactate 50 μg/mL None 0 60° C.; 2Dehydrogenase 10 min Lactate 50 μg/mL Trehalose 20 60° C.; 2Dehydrogenase 10 min Lactate 50 μg/mL Gum 33 60° C.; 23 DehydrogenaseArabic 10 min Glucose-6- 50 μg/mL None 0 50° C.; 0 phosphate 10 mindehydrogenase Glucose-6- 50 μg/mL Gum 33 50° C.; 5 phosphate Arabic 10min dehydrogenase Glucose-6- 50 μg/mL Guar 20 50° C.; 60 phosphate Gum10 min dehydrogenase Glucose-6- 50 μg/mL Trehalose 20 50° C.; 20phosphate 10 min dehydrogenase

[0065] As shown in Table 8, various proteins are stabilized againstaccelerated heat stress by different polysaccharide gums. In a specificexample, while glucose-6-phosphate dehydrogenase is not stabilizedsignificantly by gum Arabic, another polysaccharide, gum guar providesgood stability. Thus it is possible to stabilize different proteinsusing different polysaccharides. Thus, in a general embodiment, thestabilization of various proteins by polysaccharides is not limited tothe ones given in the above examples.

Example 5

[0066] Commercial gum arabic was purified by a sequence of dialysis,filtration, and lyophilization. Dialysis was performed by first making a9% solution of gum arabic in deionized water, homogenizing the sample,and then adjusting the pH to 7.4 with 1 M sodium hydroxide. The solutionwas put into 10,000 molecular weight cut-off dialysis tubing anddialyzed at 4° C. twice against PBS and twice against deionized water.The sample was then centrifuged and the supernatant filtered through a0.22 μm filter, and lyophilized.

Example 6

[0067] Following the procedures described in Example 1, aliquots ofinterferon-γ (0.02 mg/mL) were incubated at 37° C. in PBS with 0.1%azide that contained no stabilizers, 33% purified gum arabic, and 50%purified gum arabic (described in Example 5). Following incubation,samples were diluted in PBS that contained 0.5% BSA and 0.05% Tween 20.The activity of the interferon-γ in the sample was then measured usingan enzyme linked immunosorbent assay that has been shown to correspondto the bioactivity (Mechanisms of Ageing and Development, 121, 47-58(2000). The data is presented in Table 9 and FIG. 1. TABLE 9 ThermalStabilization of Interferon-γ By Gum Arabic at 37° C. and pH 7.4Activity Activity Activity Protein + Gum Arabic (GA) 1 Week 2 Weeks 4Weeks Interferon-γ + 33% GA^(a) 106 ± 17% 62 ± 15% 40 ± 13%Interferon-γ + 50% GA^(b) 133% 97% 133% Interferon-γ Control^(b)  1%  1% 9% (no stabilizers)

Example 7

[0068] This example illustrates the ability of gum arabic to stabilizeproteins against metal catalyzed oxidation (MCO) reactions. Lactatedehydrogenase is a tetrameric enzyme that catalyzes the conversion ofpyruvate to lactate in the presence of NADH. The enzymatic activity ofLDH is affected in the presence of oxidants and is catalyzed by thepresence of trace amounts of metal ions in buffers. LDH, 10⁻⁵ mM or 1.4μg/ml, was prepared in 80 mM phosphate buffer containing 0.2M potassiumchloride. MCO reactions were carried out with 0.04 mM Cupric Sulfate, 2mM ascorbic acid (Asc) in the presence or absence of 2 mM hydrogenperoxide (H₂O₂). All reactions were initiated by the addition of thereductant (ascorbic acid) or oxidant (hydrogen peroxide). The reactionmixture was incubated at room temperature for 15 minutes and assayedusing the following protocol for a 96-well plate reader. A 2.64 mM NADHand 4 mM Sodium pyruvate stock solutions were made in 0.1M phosphatebuffer, pH 7.3. All LDH solutions were diluted to 0.5 ug/ml from the MCOreactions. Two hundred μl LDH and 25 μl NADH were mixed in a microtiterplate. The reaction was initiated by adding 751 of sodium pyruvate anddecrease in absorbance at 340 nm was monitored for 10 minutes. Theresults are tabulated in Table 10 and shown in FIGS. 2 and 3. FIG. 2illustrates the stabilization of lactate dehydrogenase (LDH) againstoxidative stress caused by copper (Cu²⁺)+ascorbic acid (Asc) withdifferent concentrations of gum arabic (GA). FIG. 3 illustrates thestabilization of lactate dehydrogenase (LDH) against oxidative stresscaused by copper (Cu²⁺)+ascorbic acid (Asc)+hydrogen peroxide (H₂O₂)with different concentrations of gum arabic (GA). TABLE 10 StabilizingLactate dehydrogenase (LDH) against Oxidative Stress. ReactionConditions % Activity LDH 100 LDH + Cu²⁺ + Ascorbic Acid 2 LDH + Cu²⁺ +Ascorbic Acid + 50% GA 121 LDH + Cu²⁺ + Ascorbic Acid + 33% GA 75 LDH +Cu²⁺ + Ascorbic Acid + 10% GA 37 LDH + Cu²⁺ + Ascorbic Acid + 2% GA 1LDH + Cu²⁺ + Ascorbic Acid + H₂O₂ 1 LDH + Cu²⁺ + Ascorbic Acid + H₂O₂ +50% GA 102 LDH + Cu²⁺ + Ascorbic Acid + H₂O₂ + 33% GA 48 LDH + Cu²⁺ +Ascorbic Acid + H₂O₂ + 10% GA 2 LDH + Cu²⁺ + Ascorbic Acid + H₂O₂ + 2%GA 1

[0069] As seen in Table 10, gum arabic at 50% is an effective stabilizeragainst oxidative degradation of chymotrypsin. The stabilizationdecreases as the concentration of gum arabic decreases.

[0070] Referring now to FIG. 4, a preferred method for stabilizing aprotein used in a drug delivery system includes the steps of providing aprotein as an aqueous solution; adding at least one polysaccharide gumto the protein to form an aqueous solution or gel and adding thesolution or the gel to a delivery system 40. The delivery system 40typically comprises a capsule 41, wherein the capsule 41 furthercomprises a porous semipermeable or molecular membrane 43. The capsule41 is fabricated from a biocompatible material, and typically containsthe protein 45 and polysaccharide gum 47 in a fixed volume, preventingthe gum 47 from swelling when exposed to an aqueous environment. Themembrane 43 of the capsule 41 is fabricated from silica or a polymer andcomprises pores 49 of a size that make the membrane 43 permeable to theproteinaceous materials but impermeable to the larger polysaccharidegum. The rate at which the protein diffuses from the capsule 41 can becontrolled by the viscosity of the gum as well as by the permeability ofthe membrane 43. Further advantages of the present invention will becomeapparent to those of ordinary skill in the art upon reading andunderstanding the detailed description herein of the preferredembodiments.

EXAMPLE 8

[0071] This example illustrates chymotrypsin release through a 100Kmembrane using a 30% gum arabic, 5% gum guar or 5% locust bean gumsolution. The release of chymotrypsin from the polysaccharide gums wasevaluated because release of proteinaceous materials from themicrocapsule is an essential requirement for the gums to be used forprotein delivery, Referring now to FIGS. 5 and 6, chymotrypsin wasdissolved in a solution containing 30% gum arabic and added to capsules63 that contained 100K molecular weight cut off dialysis membranes. Theprotein diffuses out of the viscous polysaccharide, through the membrane67, and into the exchange buffer solution 68 at approximately 85% of therate at which chymotrypsin diffuses from aqueous buffer through themembrane. The rates at which chymotrypsin diffuses through guar gum andlocust bean gum through the membrane 67 are approximately 20% of therate obtained with an aqueous control. This indicates that guar andlocust bean gums can be used to significantly reduce the rate of proteindelivery through a membrane device, in addition to providingstabilization for the protein. Additionally, mixtures of various gumscan effectively be used to stabilize and control the release oftherapeutic proteins from implantable capsules.

[0072]FIG. 6 illustrates the system 60 used for evaluating usedchymotrypsin release. A falcon tube 61 was fitted with a capsule 63containing the chymotrypsin and gum materials 64. A cap 65 having a holefitted with membrane 67 allowed for diffusion of chymotrypsin into anexchange buffer 68. A magnetic stir bar 69 provided for thorough mixingof the exchange buffer 68.

[0073] The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A heat stable aqueous solution or gel comprisinga biologically effective amount of a protein and a stabilizing effectiveamount of a polysaccharide gum material.
 2. A heat stable aqueoussolution or gel according to claim 1 containing one or more minoramounts of a pharmaceutically acceptable excipient.
 3. A heat stableaqueous solution or gel according to claim 1 wherein said proteincomprises an enzyme, an antibody, a hormone, a growth factor, and acytokine.
 4. A heat stable aqueous solution or gel according to claim 3wherein said protein is a hormone.
 5. A heat stable aqueous solution orgel according to claim 3 wherein said protein is a cytokine.
 6. A heatstable aqueous solution or gel according to claim 1 wherein said gumcomprises gum arabic, guar gum, xanthan gum, locust bean gum, tragacanthgum, gum karaya, and gum ghatti.
 7. A heat stable aqueous solution orgel according to claim 6 wherein said gum is gum arabic.
 8. A heatstable aqueous solution or gel according to claim 6 wherein said gum ispresent at from about 5%(w/v) to about 50%(w/v) or the gum's solubilitylimit, and wherein when gum Arabic is selected, the concentration isover 10%(w/v).
 9. A heat stable aqueous solution or gel according toclaim 8 wherein said gum is present above 10%(w/v) to about 50%(w/v), orthe gum's solubility limit.
 10. A heat stable aqueous solution or gelaccording to claim 9 wherein said gum is present at from about 20% (w/v)to about 50% (w/v), or the gum's solubility limit.
 11. A heat stableaqueous solution or gel according to claim 2 wherein saidpharmaceutically acceptable excipient is selected from the groupconsisting of antioxidants, preservatives and surface active agents. 12.A heat stable aqueous solution or gel for use in an implantable drugdelivery device comprising a pharmaceutically effective amount of aprotein and a stabilizing effective amount of a polysaccharide gummaterial.
 13. A heat stable solution or gel according to claim 12wherein said stabilized solution or gel contains one or more minoramounts of a pharmaceutically acceptable excipient.
 14. A heat stableaqueous solution or gel according to claim 13 wherein saidpharmaceutically acceptable excipient is selected from the groupconsisting of antioxidants, preservatives and surface active agents. 15.A heat stable aqueous solution or gel according to claim 12 wherein saidprotein is selected from the group consisting of an antibody, a hormone,a growth factor, and a cytokine.
 16. A heat stable aqueous solution orgel according to claim 15 wherein said protein is a hormone or a growthfactor.
 17. A heat stable aqueous solution or gel according to claim 15wherein said protein is a cytokine.
 18. A heat stable aqueous solutionor gel according to claim 12 wherein said gum is selected from the groupconsisting of gum arabic, guar gum, xanthan gum, locust bean gum,tragacanth gum, gum karaya, and gum ghatti.
 19. A heat stable aqueoussolution or gel according to claim 18 wherein said gum is gum arabic.20. A heat stable aqueous solution or gel according to claim 18 whereinsaid gum is present at from about 5% (w/v) to about 50% (w/v) or thegum's solubility limit.
 21. A heat stable aqueous solution or gelaccording to claim 20 wherein said gum is present at from about 10%(w/v) to about 50% (w/v) or the gum's solubility limit.
 22. A heatstable aqueous solution or gel according to claim 21 wherein said gum ispresent at from about 20% (w/v) to about 50% (w/v) or the gum'ssolubility limit
 23. A lyophilized composition having biologicalactivity, wherein said lyophilized composition is formed by lyophilizinga heat stable solution or gel comprising a biologically effective amountof a protein and a stabilizing effective amount of a polysaccharide gummaterial.
 24. The lyophilized composition according to claim 23, whereinthe lyophilized polysaccharide and protein dry particles arereconstituted in an aqueous buffer in a manner so as to get highconcentration of gum that stabilizes the protein.
 25. A lyophilizedcomposition according to claim 23, wherein the said lyophilized powderis added to an implantable device that controls the release oftherapeutic protein.
 26. A lyophilized composition according to claim23, wherein the lyophilized powder is reconstituted in an aqueous bufferto provide high concentrations of the polysaccharide that will stabilizethe said therapeutic protein, and this reconstituted aqueous gum gel orsolution is further added to an implantable device.
 27. A lyophilizedcomposition according to claim 23 wherein said protein is selected fromthe group consisting of an enzyme, an antibody, a hormone, a growthfactor, and a cytokine.
 28. A lyophilized composition according to claim23 wherein said gum is selected from the group consisting of gum arabic,guar gum, xanthan gum, locust bean gum, tragacanth gum, gum karaya, andgum ghatti.
 29. A lyophilized composition according to claim 28 whereinsaid gum is gum arabic.
 30. A lyophilized composition according to claim28 wherein said gum is present at from about 5% to about 50% (w/v) afterreconstitution in aqueous buffer, or the solubility limit of the gum,and wherein when gum arabic is selected said gum is present at greaterthan 10% (w/v).
 31. A lyophilized composition according to claim 30wherein said gum is present at from about 10% (w/v) to from about 50%(w/v) after reconstitution in aqueous buffer.
 32. A lyophilizedcomposition according to claim 31 wherein said gum is present at fromabout 20% (w/v) to from about 50% (w/v) after reconstitution in aqueousbuffer.
 33. A lyophilized composition according to claim 23 optionallycontaining one or more pharmaceutically acceptable excipients.
 34. Animplantable drug delivery device containing a heat stable aqueoussolution or gel comprising a pharmaceutically effective amount of aprotein and a stabilizing effective amount of a polysaccharide gummaterial.
 35. An implantable drug delivery device containing alyophilized powder according to claim
 23. 36. An implantable drugdelivery device that is filled with a lyophilized powder according toclaim 23 that has been reconstituted with an aqueous buffer to provide athermally stabilizing amount of polysaccharide and pharmaceuticallyacceptable amount of therapeutic protein.
 37. An implantable drugdelivery device according to claim 32 wherein said stabilized solutionor gel contains one or more minor amounts of a pharmaceuticallyacceptable excipient.
 38. An implantable drug delivery device accordingto claim 33 wherein said pharmaceutically acceptable excipient isselected from the group consisting of antioxidants, preservatives andsurface active agents.
 39. An implantable drug delivery device accordingto claim 32 wherein said protein is selected from the group consistingof an antibody, a hormone, a growth factor, and a cytokine.
 40. Animplantable drug delivery device according to claim 35 wherein saidprotein is a hormone or a growth factor.
 41. An implantable drugdelivery device according to claim 32 wherein said gum is selected fromthe group consisting of gum arabic, guar gum, xanthan gum, locust beangum, tragacanth gum, gum karaya, and gum ghatti.
 42. An implantable drugdelivery device according to claim 37 wherein said gum is gum arabic.43. An implantable drug delivery device according to claim 37 whereinsaid gum is present at from about 5% (w/v) to from about 50% (w/v) orthe gum's solubility limit.
 44. An implantable drug delivery deviceaccording to claim 39 wherein said gum is present at from about 10%(w/v) to about 50% (w/v) or the gum's solubility limit.
 45. Animplantable drug delivery device according to claim 40 wherein said gumis present at from about 20% (w/v) to about 50% (w/v) or the gum'ssolubility limit.
 46. An implantable drug delivery device according toclaim 40 wherein said gum is present at from about 30% (w/v) to about50% (w/v) or the gum's solubility limit.
 47. An implantable drugdelivery device according to claim 40 wherein said gum is present atfrom about 40% (w/v) to about 50% (w/v) or the gum's solubility limit.48. An aqueous solution or gel stable against metal catalized oxidationreactions comprising a biologically effective amount of a protein and astabilizing effective amount of a polysaccharide gum material.
 49. Theoxidation stable solution or gel according to claim 48, wherein when gumarabic is selected said gum is present above about 30%(w/v) to the gumssolubility limit.